The present invention relates generally to devices for applying coatings starting from flowing or "flowable" substances such as, for example, creamy substances. The invention has been developed with particular concern for its possible use for applying food coatings constituted by flowing food substances such as, for example, melted chocolate, chocolate-flavoured creams, more or less liquid icings, decorative creamy coatings containing chopped products such as hazel-nuts, almonds, coconut, etc.
Many pastry products have coatings of this type. For example, products currently known as cream puffs or profiteroles are constituted essentially by an approximately spherical, hollow body of baked pastry or wafer filled with cream (usually held in a pleated paper cup) the top of which is coated with a creamy decorative coating which is often intended to solidify after application.
The application of this coating industrially and automatically, that is without the need for human intervention, is difficult due to various factors.
In the first place, the quality of the final result is closely dependent on the viscosity of the coating during application.
If the viscosity is too high (that is, if the coating is too dense and pasty) it is difficult to achieve a good distribution over the product which serves as the substrate: in practice, the coating, instead of adhering to the product on which it is deposited, tends to form an independent mass overlying the product itself.
If the viscosity is too low (that is, if the coating is too liquid) the coating tends to distribute itself irregularly over the product forming preferential pouring lines whereby the lower part of the coated product (that within the cup) becomes soiled without the upper part being covered sufficiently.
If the coating used is chocolate or chocolate based there is a further problem due to the fact that, in order to obtain a really satisfactory result from a qualitative point of view, it is necessary for the coating to undergo a proper hardening treatment (which usually occurs in a narrow temperature range around 29.degree. C.) without giving rise to streaks or spots. This means that the chocolate coating being applied must be kept precisely at a temperature around the hardening temperature, which is particularly difficult and expensive to achieve industrially.